The invention relates to an apparatus for tensioning a seatbelt.
In a known apparatus for tensioning a seatbelt, taught for example in EP 0 685 371 B1, the tensioner drive consists of a guide tube and a piston driven therein. The piston is connected to a traction cable that is connected via a cable guide to a seatbelt buckle. When the piston is driven linearly through the guide tube, for example by an ignited pyrotechnic propellant, the safety belt buckle is retracted and the belt webbing of the seatbelt is tensioned on a vehicle occupant""s body.
A traction cable is connected to the belt webbing and is looped round the cable guide by about 180xc2x0. The portion of traction cable extending between the cable guide and the belt webbing is guided substantially parallel to the axial direction of the guide tube, i.e. parallel to the driving direction of the piston connected to the traction cable. The traction cable, in the region of the webbing end of the pelvic belt is able to act on the belt webbing of the seatbelt, for example by means of a loop, eyelet or the like. The traction cable can also be rigidly connected to the webbing end of the pelvic belt. The belt webbing is guided round a webbing guide so that, when tensioned, it is pulled substantially parallel to the guide tube in the opposite direction to the driven piston. The cable guide is arranged at one end of the guide tube and the webbing guide at the other end of the guide tube.
Preferably, the invention allows tensioning of the seatbelt webbing at the anchor and therefore direct tensioning of the pelvic belt. The benefit of tensioning of the pelvic belt is to keep the vehicle occupant from bouncing around during a collision. The tensioning apparatus is integrated into the seatbelt anchor, which is anchored on the vehicle body, for example on the sill of the vehicle or on the vehicle seat. The piston/cylinder arrangement of the tensioner drive, the cable guide, and the webbing guide preferably form a force absorbing unit. Preferably the guide tube and the two guides are rigidly connected to one another for this purpose. The individual components can also be fastened on a load-carrying frame or housing. The vertical axes of the guide axes preferably extend substantially parallel to one another. The unit simultaneously forms the end fitting or the anchor for the pelvic belt on the vehicle body, this anchor on the vehicle body preferably being provided on the sill of the motor vehicle. The anchor can also be arranged in a stationary manner on the seat substructure.
To achieve a compact arrangement of the belt webbing which is moved along the guide tube during tensioning, a shaping device, for example in the form of a metal guide plate can be provided, by means of which the belt webbing is shaped to the contours of the external surface of the guide tube during the tensioning operation.
Advantageously the belt webbing can be sewn to the traction cable in the region of the connection in such a way that its shape is adapted to the shape of the external surface of the guide tube.